1. Field
Example embodiments relate to an over-voltage protection circuit and method thereof, for example, an over-voltage protection circuit and method detecting an over-voltage using a delay time.
2. Description of the Related Art
Over-voltage protection circuits may be used to prevent reliability deterioration of a digital logic circuit generated when a voltage greater than a predetermined or given voltage is applied to a digital logic circuit in a System On Chip (SOC). For example, in a 5V logic high system, when a voltage greater than about 6V is applied to a certain digital logic circuit, the reliability may deteriorate, and this voltage greater than 6V may be referred to as an “over-voltage”.
FIG. 1 is a block diagram schematically illustrating an example system including a conventional over-voltage protection circuit 10.
Referring to FIG. 1, the over-voltage protection circuit 10 may determine whether a supply voltage USB is an over-voltage. The over-voltage protection circuit 10 may apply the supply voltage USB to a System On Chip (SOC) 20 when the supply voltage USB is not an over-voltage.
The over-voltage protection circuit 10 may be implemented as an independent chip separate from the SOC 20. However, if the over-voltage protection circuit 10 is implemented in this way, the unit cost of the chip and the layout size of the system may increase. Thus, the increase in chip unit cost may make the system's price less competitive and the increase in system layout size may require further minimization and integration.
Also, when the supply voltage USB changes rapidly, for example, within several nano-seconds, the over-voltage protection circuit 10 may not be able to correctly detect the voltage level of the supply voltage USB.
FIG. 2 is a graph illustrating an example change in voltage with respect to time when a failure to detect operation occurs in the conventional over-voltage protection circuit 10.
Referring to FIGS. 1 and 2, if no load current exists, when a supply voltage USB of 15V is applied to the over-voltage protection circuit 10, the supply voltage USB may temporarily slew within 100 ns. In this case, the over-voltage protection circuit 10 may not generate a normal output when the supply voltage USB changes rapidly.
That is, the over-voltage protection circuit 10 may not be able to cut off the supply voltage USB of 15V in a predetermined or given time after t1, which may result in losing the over-voltage protection control function with respect to the SOC 20. The temporary loss of the over-voltage protection control function may cause significant damage to the SOC 20.